Pharmacokinetic and pharmacodynamic evaluation of intermittent versus continuous alendronate administration in rats

Magnetic solid phase extraction followed by in-situ derivatization with core-shell structured titanium dioxide coated ferriferrous oxide microspheres for determination of alendronate in plasma

In this study, for the first time, magnetic solid phase extraction (MSPE) was combined with in-situ derivatization to determine alendronate in plasma. TiO₂ coated Fe₃O₄ microspheres (denoted as Fe₃O₄@TiO₂) were synthesized via polydopamine coating, titanium ions immobilizing and calcination steps. The as-prepared microspheres could selectively extract alendronate and be quickly isolated from plasma. The drug-adsorbed Fe₃O₄@TiO₂ microspheres were then directly incubated in derivatization reagent solution to perform novel in-situ derivatization and elution procedure, in which the derivatized alendronate lost its affinity to TiO₂ and was spontaneously eluted for further LC-MS/MS detection. Satisfactory results were obtained on the creative attempt to couple dispersive magnetic solid phase extraction with in-situ derivatization. The developed method was validated and demonstrated good linearity (0.05-500 ng mL^-1), low detection limit (20 pg mL^-1), great accuracy (100.6% to 105.3%) and precision (RSDs<5.27%). Manual operation and analysis time could be greatly reduced compared to other reported methods. The method was successfully applied to a pharmacokinetic study in beagle dogs.

Effects of Bisphosphonates on Glucose Transport in a Conditionally Immortalized Rat Retinal Capillary Endothelial Cell Line (TR-iBRB Cells)

The objective of the present study was to elucidate the effect of bisphosphonates, anti-osteoporosis agents, on glucose uptake in retinal capillary endothelial cells under normal and high glucose conditions. The change of glucose uptake by pre-treatment of bisphosphonates at the inner blood-retinal barrier (iBRB) was determined by measuring cellular uptake of [³H]3-O-methyl glucose (3-OMG) using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB cells) under normal and high glucose conditions. [³H]3-OMG uptake was inhibited by simultaneous treatment of unlabeled D-glucose and 3-OMG as well as glucose transport inhibitor, cytochalasin B. On the other hand, simultaneous treatment of alendronate or pamidronate had no significant inhibitory effect on [³H]3-OMG uptake by TR-iBRB cells. Under high glucose condition of TR-iBRB cells, [³H]3-OMG uptake was increased at 48 h. However, [³H]3-OMG uptake was decreased significantly by pre-treatment of alendronate or pamidronate compared with the values for normal and high glucose conditions. Moreover, geranylgeraniol (GGOH), a mevalonate pathway intermediate, increased the uptake of [³H]3-OMG reduced by bisphosphonates pre-treatment. But, pre-treatment of histamine did not show significant inhibition of [³H]3-OMG uptake. The glucose uptake may be down regulated by inhibiting the mevalonate pathway with pre-treatment of bisphosphonates in TR-iBRB cells at high glucose condition.

Efficacy, tolerability and safety of once-monthly administration of 75mg risedronate in Japanese patients with involutional osteoporosis: a comparison with a 2.5mg once-daily dosage regimen

Oral risedronate has been shown to be effective in the treatment of osteoporosis when administered once-daily or once-weekly in Japan. This randomized, double-blind, multicenter 12-month study was conducted to compare the efficacy and tolerability of oral risedronate 75mg once-monthly with 2.5mg once-daily in Japanese patients with involutional osteoporosis. Bone mineral density (BMD), biochemical markers of bone metabolism, fractures, and adverse events (AEs) were evaluated. At the end of the study (Month 12, last observation carried forward [M12, LOCF]), mean percent change (SD) from baseline in lumbar spine (L2-L4) BMD, measured by dual energy X-ray absorptiometry (primary endpoint), was increased by 5.69 (4.00)% in the 2.5mg once-daily group (n=428), and 5.98 (4.54)% in the 75mg once-monthly group (n=422). In the non-inferiority t-test (non-inferiority margin Δ=1.5%), the 75mg once-monthly group was non-inferior to the 2.5mg once-daily group (p<0.0001). The difference between treatment groups was 0.28% (95% CI, -0.31% to 0.88%). Changes in biochemical markers of bone metabolism were generally comparable in the two groups, although decreases in the percent change from baseline in urinary NTX/CRN and CTX/CRN were statistically greater in the 2.5mg once-daily group than the 75mg once-monthly group. The frequency of new vertebral fractures (including aggravation of prevalent fractures) at the end of the study (M12, LOCF) was also similar in the two groups: 1.2% in the 2.5mg once-daily group and 1.3% in the 75mg once-monthly group. The incidence of mild/moderate/severe AEs was 75.5%/6.3%/0.5% in the 2.5mg once-daily group and 77.7%/8.1%/0.7% in the 75mg once-monthly group. AEs associated with gastrointestinal symptoms occurred in approximately 30% of subjects in each group but with no severe cases. AEs potentially associated with acute phase reaction (including symptoms of influenza-like illness or pyrexia starting within 3days of the first dose of the study drug and with a duration of 7days or less) only occurred in the 75mg once-monthly group (2.1%, 9/422 subjects; influenza-like symptoms in 1 subject and pyrexia in 8 subjects), although the incidence was low without any severe cases. In conclusion, risedronate 75mg once-monthly (a dosage which is 30 times higher than risedronate 2.5mg once-daily) had non-inferior efficacy in terms of BMD and was similarly well tolerated compared to the once-daily regimen in Japanese patients with involutional osteoporosis. Consistent with the once-daily and once-weekly dosage, the once-monthly dosage of risedronate 75mg was half that used outside Japan (150mg).

Protein isoprenylation regulates osteogenic differentiation of mesenchymal stem cells: effect of alendronate, and farnesyl and geranylgeranyl transferase inhibitors

BACKGROUND AND PURPOSE

Protein isoprenylation is an important step in the intracellular signalling pathway conducting cell growth and differentiation. In bone, protein isoprenylation is required for osteoclast differentiation and activation. However, its role in osteoblast differentiation and function remains unknown. In this study, we assessed the role of protein isoprenylation in osteoblastogenesis in a model of mesenchymal stem cells (MSC) differentiation.

EXPERIMENTAL APPROACH

We tested the effect of an inhibitor of farnesylation [farnesyl transferase inhibitor-277 (FTI-277)] and one of geranylgeranylation [geranylgeranyltransferase inhibitor-298 (GGTI-298)] on osteoblast differentiating MSC. In addition, we tested the effect of alendronate on protein isoprenylation in this model either alone or in combination with other inhibitors of isoprenylation.

KEY RESULTS

Initially, we found that levels of unfarnesylated proteins (prelamin A and HDJ-2) increased after treatment with FTI-277 concomitantly affecting osteoblastogenesis and increasing nuclear morphological changes without affecting cell survival. Furthermore, inhibition of geranylgeranylation by GGTI-298 alone increased osteoblastogenesis. This effect was enhanced by the combination of GGTI-298 and alendronate in the osteogenic media.

CONCLUSIONS AND IMPLICATIONS

Our data indicate that both farnesylation and geranylgeranylation play a role in osteoblastogenesis. In addition, a new mechanism of action for alendronate on protein isoprenylation in osteogenic differentiating MSC in vitro was found. In conclusion, protein isoprenylation is an important component of the osteoblast differentiation process that could constitute a new therapeutic target for osteoporosis in the future.

Alendronate affects calcium dynamics in cardiomyocytes in vitro

Therapy with bisphosphonates, including alendronate (ALN), is considered a safe and effective treatment for osteoporosis. However, recent studies have reported an unexpected increase in serious atrial fibrillation (AF) in patients treated with bisphosphonates. The mechanism that explains this side effect remains unknown. Since AF is associated with an altered sarcoendoplasmic reticulum calcium load, we studied how ALN affects cardiomyocyte calcium homeostasis and protein isoprenylation in vitro. Acute and long-term (48h) treatment of atrial and ventricular cardiomyocytes with ALN (10(-8)-10(-6)M) was performed. Changes in calcium dynamics were determined by both fluorescence measurement of cytosolic free Ca(2+) concentration and western blot analysis of calcium-regulating proteins. Finally, effect of ALN on protein farnesylation was also identified. In both atrial and ventricular cardiomyocytes, ALN treatment delayed and diminished calcium responses to caffeine. Only in atrial cells, long-term exposure to ALN-induced transitory calcium oscillations and led to the development of oscillatory component in calcium responses to caffeine. Changes in calcium dynamics were accompanied by changes in expression of proteins controlling sarcoendoplasmic reticulum calcium. In contrast, ALN minimally affected protein isoprenylation in these cells. In summary, treatment of atrial cardiomyocytes with ALN-induced abnormalities in calcium dynamics consistent with induction of a self-stimulatory, pacemaker-like behavior, which may contribute to the development of cardiac side effects associated with these drugs.

Effect of alpha tocopherol acetate in Walker 256/B cells-induced oxidative damage in a rat model of breast cancer skeletal metastases

The pathophysiological changes and the oxidative-antioxidative status were evaluated in the bone microenvironment of rat inoculated with Walker 256/B mammary gland carcinoma cells, and used alpha-tocopherol acetate (ATA) as a countermeasure. Walker 256/B cells were injected into the right femora of aged male rats. Animals were randomized into three groups: 12 rats were injected with saline (control group); 14 rats were injected with Walker 256/B cells (5x10(4)) in the medullar cavity (W256 group); 14 rats were inoculated with Walker 256/B cells and treated with ATA (45mg/kg BW) (W256+ATA group). After 20 days, rats were euthanized and the femurs were radiographed. Micro architectural parameters were measured by microcomputed tomography and histology. Serum, bone and bone marrow were evaluated for oxidative damage. In parallel, cell cultures were done in the presence of ATA and ROS were measured by fluorescence; apoptotic cells were determined in parallel. W256 groups had osteolytic damages with marked resorption of cortical and trabecular bone. W256+ATA animals presented marked osteosclerotic areas associated with tumor necrosis areas inside the bone cavity. Levels of lipid peroxidation and protein oxidation were found to increase in W256 rats; a significant reduction in SOD and GSH-p activities was also observed. W256+ATA group had significantly reduced oxidative damage, but not reversed back to the control levels. The present study shows that Walker 256/B cells induce skeletal metastases associated with oxidative damage in the bone microenvironment. ATA reduced the oxidative stress damage, enhanced osteosclerosis and tumor cell apoptosis both in vitro and in vivo.

Radiographic and histological evaluation of bisphosphonate alendronate and metotrexate effects on rat mandibles inoculated with Walker 256 carcinosarcoma

PURPOSE

To investigate the effects of bisphosphosnate alendronate (ALD) and metotrexate (MTX) on an experimental model of Walker 256 carcinosarcoma developed in the oral cavity of rats. METHODS Walker 256 carcinosarcoma cell suspension (0,1 mL) containing 10(6) cell/mL was implanted in the alveoli of the first and second molars. The animals were divided and treated with saline, MTX, ALD, and MTX plus ALD. Later, the animals were sacrificed, the tumors were measured and the mandibles were removed for radiographic and histological analysis.

RESULTS

In the control group, the radiographic images demonstrated radioluscency with poorly defined borders, and the microscopic examination revealed tumor infiltration into the peripheral and central regions of the bone. Areas of necrosis were commonly seen. In the treated groups with ALD, associated or not with MTX, the radiographic analysis revealed circumscribed tumor-induced osteolysis and various degrees of radiotransparence; while, histologically, preserved bone trabeculae with osteoid formation was observed among malignant cells.

CONCLUSION

The bisphosphonate alendronate exherted an osteoprotective effect and induced bone neoformation on the Walker 256 carcinosarcoma inoculated in rat mandibles. The combination of metotrexate with bisphosphonate alendronate is more successful than treatment with the agents alone in controlling the growth of neoplastic cells and in stimulating reactive new bone. Therefore, this may be an alternative treatment to malignant lesions of maxillaries with osteolysis.

Effect of short-term treatment with alendronate on ulnar bone adaptation to cyclic fatigue loading in rats

Targeted remodeling of fatigue-injured bone involves activation of osteoclastic resorption followed by local bone formation by osteoblasts. We studied the effect of parenteral alendronate (ALN) on bone adaptation to cyclic fatigue. The ulnae of 140 rats were cyclically loaded unilaterally until 40% loss of stiffness developed. We used eight treatment groups: (1) baseline control; (2) vehicle (sterile saline) and (3) alendronate before fatigue, no adaptation (Pre-VEH, Pre-ALN, respectively); (4) vehicle and (5) alendronate during adaptation to fatigue (Post-VEH, Post-ALN, respectively); (6) vehicle before fatigue and during adaptation (Pre-VEH/Post-VEH); (7) alendronate before fatigue and vehicle during adaptation (Pre-ALN/Post-VEH); (8) alendronate before fatigue and during adaptation (Pre-ALN/Post-ALN). Bones from half the rats/group were tested mechanically; remaining bones were examined histologically. The following variables were quantified: volumetric bone mineral density (vBMD); ultimate force (F(u)); stiffness (S); work-to-failure (U); cortical area (Ct.Ar); new woven bone tissue area (Ne.Wo.B.T.Ar); resorption space density (Rs.N/T.Ar). Microcracking was only seen in fatigue-loaded ulnae. A significant effect of alendronate on vBMD was not found. Preemptive treatment with alendronate did not protect the ulna from structural degradation during fatigue. After fatigue, recovery of mechanical properties by adaptation occurred; here a significant alendronate effect was not found. An alendronate-specific effect on adaptive Ne.Wo.B.T.Ar was not found. In the fatigue-loaded ulna, Rs.N/T.Ar was increased in vehicle-treated adapted groups, but not alendronate-treated adapted groups, when compared with baseline control. These data suggest that short-term alendronate treatment does not protect bone from fatigue in this model. Inhibition of remodeling may reduce microcrack repair over time.

Acrylic injectable and self-curing formulations for the local release of bisphosphonates in bone tissue

Two bisphosphonates (BPs), namely 1-hydroxy-2-[4-aminophenyl]ethane-1,1-diphosphonic acid (APBP) and 1-hydroxy-2-[3-indolyl]ethane-1,1-diphosphonic acid (IBP), have been synthesized and incorporated to acrylic injectable and self-curing formulations. Alendronic acid monosodium trihydrated salt (ALN) containing cement was formulated as control. These systems have potential applications in low density hard tissues affected by ailments characterized by a high osteoclastic resorption, i.e. osteoporosis and osteolysis. Values of curing parameters of APBP and IBP were acceptable to obtain pastes with enough fluency to be injected through a biopsy needle into the bone cavity. Working times ranged between 8 and 15 min and maximum temperature was around 50 degrees C. Cured systems stored for a month in synthetic body fluid had compressive strengths between 90 and 96 MPa and modulus between 1.2 and 1.3 GPa, which suggest mechanical stabilization after setting and in the short time. BPs were released in PBS at an initial rate depending on the corresponding chemical structure in the order ALN > APBP > IBP to give final concentrations in PBS of 2.21, 0.44, and 0.19 mol/mL for ALN, APBP, and IBP, respectively. Cytotoxicities of bisphosphonates were evaluated, IC(50) values being in the order APBP > ALN > IBP. Absence of cytotoxicity coming from leachables of the cured systems was observed in all cases independently of the BP. An improved cell growth and proliferation for the systems loaded with APBP and IBP compared with that loaded with ALN was observed, as assessed by measuring cell adhesion and proliferation, and total DNA content.

Rat models of bone metastases

Bone metastases occur frequently in patients with advanced breast or prostate cancer. Bone metastases can be predominantly osteolytic, osteoblastic or mixed. Studies with animal models allow advances in understanding the molecular basis for bone metastases and provide new targets for therapy. Several animal models have been developed in rat with different pathophysiologies; they required injection or implantation of neoplastic cells into orthotopic locations, bones or the left ventricle of the heart. Several specific strains of rat have an increased incidence of spontaneous tumors. Carcinomas can be induced by either chemicals or physical agents. However, the most used and convenient way to induce bone metastases is a syngeneic transmission. MAT-Ly-Lu cells have been used in several models using Copenhagen rats to induce osteoblastic bone lesions. PA-III cells derived from Pollard tumors can also produce a combination of osteolytic and osteoblastic reactions at the site of transplantation. Osteolytic bone lesions can be obtained with an injection of Walker cells. The use of 13762 or c-SST2 cells allows also leads to osteolysis. Human xenografts can only be used in nude animals. It is essential to validate and correctly interpret the lesions in several models of bone metastasis. No animal model is sufficient by itself to represent the clinical findings observed in humans. The use of models developed in different species should be more predictive and bring a beam of arguments for a better knowledge of pathophysiological and therapeutic mechanisms.

The role of subchondral bone remodeling in osteoarthritis: reduction of cartilage degeneration and prevention of osteophyte formation by alendronate in the rat anterior cruciate ligament transection model

OBJECTIVE

It has been suggested that subchondral bone remodeling plays a role in the progression of osteoarthritis (OA). To test this hypothesis, we characterized the changes in the rat anterior cruciate ligament transection (ACLT) model of OA and evaluated the effects of alendronate (ALN), a potent inhibitor of bone resorption, on cartilage degradation and on osteophyte formation.

METHODS

Male Sprague-Dawley rats underwent ACLT or sham operation of the right knee. Animals were then treated with ALN (0.03 and 0.24 microg/kg/week subcutaneously) and necropsied at 2 or 10 weeks postsurgery. OA changes were evaluated. Subchondral bone volume and osteophyte area were measured by histomorphometric analysis. Coimmunostaining for transforming growth factor beta (TGF beta), matrix metalloproteinase 9 (MMP-9), and MMP-13 was performed to investigate the effect of ALN on local activation of TGF beta.

RESULTS

ALN was chondroprotective at both dosages, as determined by histologic criteria and collagen degradation markers. ALN suppressed subchondral bone resorption, which was markedly increased 2 weeks postsurgery, and prevented the subsequent increase in bone formation 10 weeks postsurgery, in the untreated tibial plateau of ACLT joints. Furthermore, ALN reduced the incidence and area of osteophytes in a dose-dependent manner. ALN also inhibited vascular invasion into the calcified cartilage in rats with OA and blocked osteoclast recruitment to subchondral bone and osteophytes. ALN treatment reduced the local release of active TGF beta, possibly via inhibition of MMP-13 expression in articular cartilage and MMP-9 expression in subchondral bone.

CONCLUSION

Subchondral bone remodeling plays an important role in the pathogenesis of OA. ALN or other inhibitors of bone resorption could potentially be used as disease-modifying agents in the treatment of OA.

Bone as an effect compartment : models for uptake and release of drugs

"Bone-seeking agents" are drugs characterised by high affinity for bone, and are disposed in bone for prolonged periods of time while maintaining remarkably low systemic concentrations. As a consequence, the bone becomes a reservoir for bone-seeking agents, and a site of both desirable and adverse effects, depending on the pharmacological activities of the specific agent. For some agents, significant systemic effects may also be produced following their prolonged release from bone, a process that is governed mostly by the rate of bone remodelling. This review covers the pharmacokinetic and pharmacodynamic features of bone-seeking agents with different pharmacological properties, including drugs (bisphosphonates, drug-bisphosphonate conjugates, radiopharmaceuticals and fluoride), bone markers (tetracycline, bone imaging agents) and toxins (lead, chromium, aluminium). In addition, drugs that do not possess bone-seeking properties but are used for therapy of bone diseases (such as antibacterials for treatment of osteomyelitis) are discussed, along with targeting of these drugs to the bone by conjugation to bone-seeking agents, local delivery systems, and other approaches. The pharmacokinetic and pharmacodynamic behaviour of bone-seeking agents is extremely complex due to heterogeneity in bone morphology and physiology. This complexity, accompanied by difficulties in human bone research caused by ethical and other limitations, gave rise to modelling approaches to study bone drug disposition. This review describes the pharmacokinetic models that have been proposed to describe the pharmacokinetic behaviour of bone-seeking agents and predict bone concentrations of these agents for different doses and patient populations. Models of different types (compartmental and physiologically based) and of different complexity have been applied, but their relevance to drug effects in the bone tissue is limited since they describe the behaviour of the "average" drug molecule. Understanding of the cellular and molecular processes responsible for the heterogeneity of bone tissue will provide better comprehension of the influence of microenvironment on drug bone disposition and the resulting pharmacological response.